Looking for experience with them being used in a winter camping environment. Bottom insulation is covered. I do not want a quilt, I don't want a different bag, I'm looking at these for specific reasons. Any experience with them is greatly helpful.

The North Face Furnace 0 Degree Down Sleeping Bag
Kelty Cosmic 0 Degree DriDown Sleeping Bag
Outdoor Vitals Summit 0 Degree Down Sleeping Bag
Marmot Never Summer Sleeping Bag 0 Degree Down